pro fftpieces, old, new
; take the output of fft and put them the way they should be.
;	must have an even number of elements in the array.

	sz = size(old)
	nx = sz(1)
	ny = sz(2)

	new = complexarr(nx,ny)

	bx = nx/2
	by = ny/2

	q1 = old(0:bx-1,0:by-1)
	q2 = old(0:bx-1,by:*)
	q3 = old(bx:*,0:by-1)
	q4 = old(bx:*,by:*)

	q1n = rotate(q1,2)
	q2n = rotate(q2,2)
	q3n = rotate(q3,2)
	q4n = rotate(q4,2)

;	q1n = complexarr(bx,by)
;	q2n = complexarr(bx,by)
;	q3n = complexarr(bx,by)
;	q4n = complexarr(bx,by)
;
;	for ii=0,bx-1 do begin
;	for jj=0,by-1 do begin
;		q1n(ii,jj) = q1(bx-1-ii,by-1-jj)
;		q2n(ii,jj) = q2(bx-1-ii,by-1-jj)
;		q3n(ii,jj) = q3(bx-1-ii,by-1-jj)
;		q4n(ii,jj) = q4(bx-1-ii,by-1-jj)
;	endfor
;	endfor

	new(0:bx-1,0:by-1) = q1n
	new(0:bx-1,by:*) = q2n
	new(bx:*,0:by-1) = q3n
	new(bx:*,by:*) = q4n

	return
	end